sand vs. vermiculite/perlite

[flashback]

I am making soil for 15 - 18 gallon containers. Would sand or vermiculite/perlite be best to use?

Thanks, John

[amideutch]

John, are you using regular soil or a soiless potting mix? For my containers I use a Rhododendron mix and add perlite plus a few other amendments. Ami

[flashback]

I will be using peat, compost and ?. The last part will be sand, perlite, or vermiculite.

[amideutch]

Either perlite or vermiculite, your choice. Ami

[flashback]

I had originally wanted to use perlite but the cost at 18.00 per 4 cu. ft. adds up. Sand 20.00 a cu. yd. sounds good but I had thought the perlite would be best. Thanks.

[gardenfrog]

Mel Bartholomew from squarefootgardening.com has a soil mixture that he swears by (used it for 10 years). It is 1/3 peat, 1/3 Vermiculite and 1/3 compost. He says you don't even need to add fertilizer, just refresh the compost every year.

[creister]

You could also try expanded shale. Like vermiculite, it will help retain water. I don't believe perlite does.

[amideutch]

Perlite has an absortion rate of about 27% for water. Vermiculite has a water retention rate of about 50%. Ami

[gardenfrog]

I'm not familiar with "expanded shale". Is that something like Mica, the stuff that gets in the way when you pan for gold?

[outsiders71]

There is no reason to avoid using sand, unless you will be moving the containers frequently. Sand adds a considerable amount of weight but IMO does a better job at aeration than perlite/vermiculite. Perlite also tends to float to the top and grow nasty green algae/mold.

I switched over to sand a few years ago. I buy the filtered, cleaned, play sand from one of the big home improvement stores. Don't use the other kinds of sand unless you clean it yourself.

[amideutch]

For containers I would stay away from sand. Can't see sand doing a better job of aeration than perlite or vermiculite. The only place I've seen perlite float was the little that was on top of the aggregate. The rest stays put inside the aggregate. And never had algae problems as the water always percolates through the aggregate. The only place you see algae is in Earthbox/Tainer type where there is a reservoir in the bottom where water accumulates and remains and the algae grows there.
As far as purchasing perlite check out e-bay or the home improvement centers where they sell it for home insulation. Same stuff as what the garden centers sell but a lot cheaper. That's where I get mine from here in Germany. Ami

[flashback]

In reading more about perlite vs. vermiculite, the vermiculite sounds best. It retains more water and is pretty much the same as far as the airation. For outside use anything that holds more water would be the better one for me.

Thanks for the help, John

[Johnnyv_44]

I've got some Pro-mix BX I'm going to use in my containers. I know its more expensive but it has everything in it already. I has Vermiculite,pearlite, dolomite and I believe Peat.

[outsiders71]

Originally Posted by amideutch

For containers I would stay away from sand. Can't see sand doing a better job of aeration than perlite or vermiculite.

Why not? The particle size of sand is significantly smaller than perlite/vermiculite, giving roots more aeration.

Perlite can hold water but its main use is to aerate the soil, not to keep it moist. Peat's job is to keep the soil moist.

If you're worried about water loss or want less frequent waterings:

1) Increase container size if possible.

2) Mulch your container.

3) Switch to COIR. It holds water better and lasts longer than peat (and if you want to open the can of worms, is more environment friendly). Go for a brand such as Botanicare Cocogro, which is rinsed and aged.

4) Add LFS (Long fiber sphagnum) to your mix. New Zealand LFS is the best quality and doesn't break down as fast as the rest. This stuff will hold water!

5) Build a container like Ray's.

[amideutch]

Sand has to be course or you will get poor drainage. Water retention of sand is questionable as little water penetrates into the grains. For growing in containers Perlite and Vermiculite are superior to sand. If your going to be growing in beds using the Mittleider method by all means use sand as an ingredient in your aggregate mix. Ami